Method for the emulsion polymerization of olefins

ABSTRACT

A method for the emulsion polymerization of one or more olefins by reacting a ligand of general formulae Ia and Ib or a mixture of at least two ligands Ia or Ib, wherein R respectively represents one or several of the following radicals; hydrogen, halogen, nitrile, C 1 -C 12 -alkyl groups, C 1 -C 12 -alkoxy groups, C 7 -C 13 -aralkyl groups, C6-C14-aryl groups, and wherein identical or different compounds of general formulae Ia and Ib can, optionally, be concatenated by one or several bridges, with a phosphine compound PR3′ and a metal compound of general formula M(L 2 ) 2  or M(L 2 ) 2  (L 1 ) z , wherein the variables are defined as follows: M is a transition metal of groups 7-10 in the periodic system of the elements; L 1  represents phosphanes (R 5 ) x PH 3-x  or amines (R 5 ) x NH 3-x  with identical or different radicals R 5 , ether (R 5 ) 2 O, H 2 O, alkohols (R 5 )OH, pyridine, pyridine derivatives of formula C 5 H 5-x (R 5 ) x N, CO, C 1 -C 12 -alkylnitriles, C 6 -C 14 -arylnitriles or ethylenically unsaturated double bond systems, wherein x is a whole number ranging from 0-3, L 2  represents halogenide ions R 6   x NH 3-x , wherein x is a whole number ranging from 0 3 and R 6  represents C 1 -C 12 -alkyl, and C 1 -C 6 -alkylane ions, allylane ions, benzylane ions or arylane ions, wherein L 1  and L 2  can be concatenated with each other by one or several covalent bonds, z is a number ranging from 0 4. The invention also relates to the immediate use of the reaction product in the polymerization or copolymerization of olefins in water or in a solvent mixture containing at least 50 vol. % water in the presence of an emulsifier and, optionally, in the presence of an activator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for the emulsionpolymerization of one or more olefins by reacting a ligand of theformula Ia or Ib or a mixture of at least two of the ligands Ia or Ib

in each of which R denotes one or more of the following radicals:

-   hydrogen-   halogen-   nitrile-   C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy, C₇-C₁₃ aralkyl, C₆-C₁₄ aryl groups,    unsubstituted or substituted by: C₁-C₁₂ alkyl groups, halogens,    C₁-C₁₂ alkoxy, C₃-C₁₂ cycloalkyl, C₁-C₁₂ thioether groups, carboxyl    groups or sulfo groups present where appropriate in the form of    their salts, and also amino groups with hydrogen and/or C₁-C₁₂ alkyl    radicals-   amino groups NR¹R², where R¹ and R² together or separately are    hydrogen, C₁-C₁₂ alkyl, C₇-C₁₃ aralkyl or C₆-C₁₄ aryl groups and may    additionally form a saturated or unsaturated 5- to 10-membered ring,    unsubstituted or substituted by: C₁-C₁₂ alkyl groups, halogens,    C₁-C₁₂ alkoxy, C₃-C₁₂ cycloalkyl, C₁-C₁₂ thioether groups, carboxyl    groups or sulfo groups present where appropriate in the form of    their salts, and also amino groups with hydrogen and/or C₁-C₁₂ alkyl    radicals-   and where identical or different compounds of the formulae Ia and Ib    may where appropriate also be bridged by one or more C₁-C₁₂    alkylene, C₂-C₁₂ alkylated azo or formula II bridges

-   where Y is silicon or germanium and R³ and R⁴ are hydrogen and/or    C₁-C₁₂ alkyl,-   with a phosphine compound PR′₃, where R′ is hydrogen, C₁-C₁₂ alkyl,    C₄-C₁₂ cycloalkyl, C₇-C₁₅ aralkyl or C₆-C₁₅ aryl groups,-   or with a diphosphine compound R′₂P-G-PR′₂, where R′ is as defined    for the phosphine compounds PR′₃ and G is C₁-C₁₂ alkyl, C₄-C₁₂    cycloalkyl, C₇-C₁₅ aralkyl or C₆-C₁₅ aryl groups,-   and also with a metal compound of the formula M(L²)₂ or    M(L²)₂(L¹)_(z),    where the variables are defined as follows:-   M is a transition metal from groups 7 to 10 of the Periodic System    of the Elements;-   L¹ is phosphanes (R⁵)_(x)PH_(3-x) or amines (R⁵)_(x)NH_(3-x) with    identical or different radicals R⁵, ethers (R⁵)₂O, H₂O, alcohols    (R⁵)OH, pyridine, pyridine derivatives of the formula    C₅H_(5-x)(R⁵)_(x)N, CO, C₁-C₁₂ alkyl nitrites, C₆-C₁₄ aryl nitriles    or ethylenically unsaturated double bond systems, x being an integer    from 0 to 3,-   R⁵ is hydrogen, C₁-C₂₀ alkyl groups, which may in turn be    substituted by O(C₁-C₆ alkyl) or N(C₁-C₆ alkyl)₂ groups, C₃-C₁₂    cycloalkyl groups, C₇-C₁₃ aralkyl radicals, and C₆-C₁₄ aryl groups,-   L² is halide ions, R⁶ _(x)NH_(3-x), where x is an integer from 0 to    3 and R⁶ is C₁-C₁₂ alkyl, and also C₁-C₆ alkyl anions, allyl anions,    benzyl anions or aryl anions, it being possible for L¹ and L² to be    linked to one another by one or more covalent bonds,-   z is a number from 0 to 4,    and using the reaction product immediately to polymerize or    copolymerize olefins in water or a solvent mixture with a water    content of at least 50% by volume in the presence of an emulsifier    and, optionally, of an activator.

The complex formed in situ does not undergo isolation and purification.

For the process of the invention it is optional to use an activator suchas, for example, olefin complexes of rhodium or of nickel. Thisinvention further relates to dispersions of polyolefins such aspolyethylene and ethylene copolymers in water, to the use of the aqueousdispersions of the invention for paper applications such as papercoating or surface sizing, paints, adhesive base materials, foammoldings such as mattresses, applications to textiles and leather,coatings on carpet backings, or pharmaceutical applications.

2. Description of the Background

Aqueous dispersions of polymers are utilized commercially in numerous,very different applications. Examples include paper applications(coating and surface sizing), base materials for paints and varnishes,adhesive base materials (including pressure sensitive adhesives),applications to textiles and leather, chemicals used in the constructionindustry, foam moldings (mattresses, coatings for carpet backings), andalso for medical and pharmaceutical products, as binders forpreparations, for example. A summary can be found in D. Distler (editor)“WäBrige Polymerdispersionen”, Wiley-VCH Verlag, 1st edition, 1999.

To date it has been difficult to prepare aqueous dispersions ofpolyolefins. It would, however, be desirable to be able to prepare suchaqueous dispersions of polyolefins, since the monomers such as ethyleneor propylene are very advantageous from an economic standpoint.

The commonplace processes for preparing such aqueous dispersions fromthe corresponding olefins make use either of free-radical high-pressurepolymerization or else of the preparation of secondary dispersions.These processes are hampered by disadvantages. The free-radicalpolymerization processes require extremely high pressures, arerestricted to ethylene and ethylene copolymers on the industrial scale,and involve an apparatus which is very expensive to purchase andmaintain. Another possibility is first to polymerize ethylene, by anydesired process, and then to prepare a secondary dispersion, asdescribed in U.S. Pat. No. 5,574,091. This method is a multistageprocess and hence is very cumbersome.

It is therefore desirable to polymerize 1-olefins such as ethylene orpropylene under the conditions of emulsion polymerization and to preparethe required dispersion in one step from the corresponding monomer.Moreover, emulsion polymerization processes have the advantage, verygenerally, that they give polymers of high molar mass, the removal ofheat being easy to manage as an inherent feature of the process. Lastly,reactions in aqueous systems very generally are of interest, on accountof the fact that water is an inexpensive and environmentally friendlysolvent.

Processes proposed to date for the emulsion polymerization of 1-olefinssuch as ethylene or propylene require further improvement. The problemgenerally resides in the catalyst which is needed to polymerize thesemonomers.

With electrophilic transition metal compounds such as TiCl₄(Ziegler-Natta catalyst) or metallocenes it is possible to polymerizeolefins, as described, for example, by H.-H. Brintzinger et al. inAngew. Chem., Int. Ed. Engl. 1995, 34, 1143. However, both TiCl₄ andmetallocenes are sensitive to moisture and are therefore poorly suitedto preparing polyolefins in emulsion polymerization. The aluminum alkylcocatalysts used are also sensitive to moisture; accordingly, water, asa catalyst poison, must be carefully excluded.

There are but few reports of transition metal catalyzed reactions ofethylene in aqueous medium. For instance, L. Wang et al. in J. Am. Chem.Soc. 1993, 115, 6999 report a rhodium catalyzed polymerization. Ataround one insertion per hour, however, the activity is much too low forindustrial applications.

The reaction of ethylene with nickel-P,O-chelate complexes appears muchmore promising, as it is described in U.S. patents U.S. Pat. No.3,635,937 and U.S. Pat. No. 3,686,159. The polymer analysis data are notreported. Additionally, the reported activity is still much too low forindustrial applications.

EP-A 0 046 331 and EP-A 0 046 328 report the reaction of ethylene withNi-chelate complexes of the formula A

where R refers to identical or different organic substituents of whichone carries a sulfonyl group and F denotes phosphorus, arsenic ornitrogen. The selected reaction conditions in solvents such as methanolor mixtures of methanol and a hydrocarbon produced only oligomers, whichare not suitable for the applications specified above.

U.S. Pat. No. 4,698,403 (column 7, lines 13-18) and U.S. Pat. No.4,716,205 (column 6, lines 59-64) show that an excess of water acts as acatalyst poison to bidentate Ni-chelate complexes, even when they carryan SO₃ ⁻ group.

From the documents cited above it is apparent that numerous Ni complexesare not active in polymerization in the presence of water.

Furthermore, WO 97/17380 discloses that palladium compounds of theformula B

where R′ stands, for example, for isopropyl groups, or the analogousnickel compounds, are able to polymerize higher olefins such as 1-octenein an aqueous environment. An option is to add an emulsifier, in orderto facilitate the polymerization. Nevertheless, it is specified that thetemperature of 40° C. should not be exceeded, since otherwise thecatalyst is deactivated (p. 25, lines 5 et seq.). Higher reactiontemperatures, however, are generally desirable, since they allow theactivity of a catalyst system to be increased.

Further drawbacks of formula B catalyst systems are that, with ethylene,highly branched polymers are generally formed (L. K. Johnson, J. Am.Chem. Soc. 1995, 117, 6414), which have been of little significanceindustrially to date, and that, with higher α-olefins, the phenomenonknown as “chain running” is inevitably observed in the active complexes.Chain running leads to a large number of 1,ω-misinsertions, as a resultof which, generally, amorphous polymers are produced, which are poorlysuited to use as materials of construction.

It is also known that complexes of the formula C

(WO 98/42665), where M=Ni or Pd, having n neutral ligands L, are activein polymerization in the presence of small amounts of water withoutdetriment to the catalytic activity (page 16, line 13). These amounts ofwater, however, must not exceed 100 equivalents, based on the complex(page 16, lines 30-31). Under these conditions, though, it is impossibleto carry out an emulsion polymerization.

It is disclosed, moreover, that complexes of the formula D

having identical or different radicals R are capable of polymerizingethylene in the presence of small amounts of water (WO 98/42664,especially page 17, lines 14 et seq.). These amounts of water, however,must not exceed 100 equivalents, based on the complex (page 17, lines33-35). Under these conditions, though, it is impossible to carry out anemulsion polymerization.

The preparation of aqueous dispersions with the aid of transition metalcatalysts is also described in EP-A 1110977 and WO 01/44325.

Furthermore, the two laid-open specifications DE-A 2923206 and DE-A3345785 each describe processes for preparing polyethylene usingcatalysts referred to as in situ catalysts, consisting of a nickelcompound and a mixture of a quinonoid compound and also a tertiaryphosphine. Neither of these documents, however, discloses that thesecatalysts can be used to prepare aqueous dispersions containingpolyethylene.

In view of the great commercial importance of polyolefins, the searchfor improved processes for polymerization continues to be of greatimportance.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved process which

-   -   polymerizes olefins in the presence of large amounts of water to        give polyolefins,    -   produces materials with very low levels of branching and with        high molecular weights, and    -   allows this reaction to be carried out under industrially        reasonable conditions.

It is a further object to use

-   -   the process of the invention to prepare aqueous polyolefin        dispersions and    -   these polyolefin dispersions for paper applications (coating and        surface sizing), base materials for paints and varnishes,        adhesive base materials (including pressure sensitive        adhesives), applications to textiles and leather, in chemicals        used in the construction industry, foam moldings (mattresses,        coatings for carpet backings), and also for medical and        pharmaceutical products.

We have found that these objects are achieved by the process defined atthe outset.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Suitable olefins for the polymerization include: ethylene, propylene,1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene and1-eicosene, and also branched olefins such as 4-methyl-1-pentene,vinylcyclohexene, and vinylcyclohexane, and also styrene,para-methylstyrene and para-vinylpyridine, preference being given toethylene and propylene. Ethylene is particularly preferred.

The copolymerization of two olefins is also possible with the process ofthe invention, the comonomer being selectable from the following groups:

-   -   1-olefins such as ethylene, propylene, 1-butene, 1-pentene,        1-hexene, 1-heptene, 1-octene, 1-decene and 1-eicosene, and also        branched olefins such as 4-methyl-1-pentene, vinylcyclohexene,        and vinylcyclohexane, and also styrene, para-methylstyrene, and        para-vinylpyridine, preference being given to propylene,        1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and        1-decene;    -   internal olefins such as norbornene, norbornadiene or cis- or        trans-2-butene;    -   polar monomers such as acrylic acid, acrylic acid C₁-C₈ alkyl        ester, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate,        4-hydroxybutyl acrylate, methacrylic acid, methacrylic acid        C₁-C₈ alkyl esters, C₁-C₆ alkyl vinyl ethers, and vinyl acetate;        preference is given to acrylic acid, methyl acrylate, ethyl        acrylate, n-butyl acrylate, 2-ethylhexyl acrylate,        2-hydroxyethyl acrylate, methyl methacrylate, ethyl        methacrylate, n-butyl methacrylate, ethyl vinyl ether, and vinyl        acetate.

The ratio of the two monomers may be chosen freely. It is preferred,however, for the comonomer to be used in fractions of from 0.1 to 20 mol%, based on the principal monomer.

In the ligands of the formulae Ia and Ib the radicals are defined asfollows:

-   R is selected from in each case one or more of the following    radicals:    -   hydrogen    -   halogens, i.e., atoms of fluorine, chlorine, bromine or iodine,        preference being given to fluorine, chlorine, and bromine    -   nitrile    -   C₁-C₁₂ alkyl groups such as methyl, ethyl, n-propyl, iso-propyl,        n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl.        sec-pentyl, neo-pentyl, 1,2-dimethylpropyl, iso-amyl, n-hexyl,        iso-hexyl, sec-hexyl, n-heptyl, iso-heptyl, n-octyl, n-nonyl,        n-decyl, and n-dodecyl; preferably C₁-C₆ alkyl such as methyl,        ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl,        tert-butyl, n-pentyl, iso-pentyl, sec-pentyl, neo-pentyl,        1,2-dimethylpropyl, iso-amyl, n-hexyl, iso-hexyl, and sec-hexyl,        with particular preference C₁-C₄ alkyl such as methyl, ethyl,        n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, and        tert-butyl    -   C₁-C₁₂ alkoxy groups such as the examples listed for C₁-C₁₂        alkyl groups but with the addition of an oxygen atom at the end        of the group (for example, methoxy, ethoxy, n-propyloxy,        iso-propyloxy, n-butyloxy)    -   C₇-C₁₃ aralkyl groups such as, for example, C₇ to C₁₂        phenylalkyl such as benzyl, 1-phenethyl, 2-phenethyl,        1-phenylpropyl, 2-phenylpropyl, 3-phenylpropyl, neophyl        (1-methyl-1-phenylethyl), 1-phenylbutyl, 2-phenylbutyl,        3-phenylbutyl, and 4-phenylbutyl, with particular preference        benzyl;    -   C₆-C₁₄ aryl groups such as, for example, phenyl, 1-naphthyl,        2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl,        2-phenanthryl, 3-phenanthryl, 4-phenanthryl, and 9-phenanthryl,        preferably phenyl, 1-naphthyl, and 2-naphthyl, with particular        preference phenyl    -   amino groups NR¹R², R¹ and R² together or separately being        hydrogen, C₁-C₁₂ alkyl groups, C₇-C₁₃ alkyl radicals or C₆-C₁₄        aryl groups (in each case as defined above) and additionally        being able to form a saturated or unsaturated 5- to 10-membered        ring; preference here is given to the dimethylamino, the        diethylamino, the diisopropylamino, the methylphenylamino, and        the dimethylamino group. Examples of amino groups of saturated        rings are the N-piperidyl group and the N-pyrrolidinyl group;        examples of amino groups with unsaturated rings are the N-pyrryl        group, the N-indolyl group, and the N-carbazolyl group.

The abovementioned radicals of C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy, C₇-C₁₃aralkyl, C₆-C₁₄ aryl, and NR¹R² amino groups may in each case be presentin unsubstituted form on the quinonoid parent structure of the formulaeIa and Ib. They may also themselves additionally carry one or else moreof the following substituents on their own molecular framework:

-   -   halogens    -   C₁-C₁₂ alkyl groups, C₁-C₁₂ alkoxy groups, amino groups with        hydrogen and/or C₁-C₁₂ alkoxy groups such as defined above in        each case;    -   C₃-C₁₂ cycloalkyl groups such as cyclopropyl, cyclobutyl,        cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl,        cyclodecyl, cycloundecyl, and cyclododecyl; preference is given        to cyclopentyl, cyclohexyl, and cycloheptyl;    -   C₁-C₁₂ thioether groups such as methylmercaptyl, ethylmercaptyl,        n-propylmercaptyl, iso-propylmercaptyl, n-butylmercaptyl,        iso-butylmercaptyl, tert-butylmercaptyl, n-pentylmercaptyl,        iso-pentylmercaptyl, neopentylmercaptyl, and n-hexylmercaptyl;    -   carboxyl groups, where appropriate in the form of their salts,        preferably their alkali metal salts, in particular in the form        of their lithium, sodium or potassium salts and also their        ammonium salts    -   sulfo groups, where appropriate in the form of their salts,        preferably their alkali metal salts, in particular in the form        of their lithium, sodium or potassium salts and also their        ammonium salts.

It is also possible to use compounds of the formulae Ia and Ib which areconnected to one another by one or more C₁-C₁₂ alkylene bridges, inparticular by one or more C₂-C₁₀ alkylene bridges, with particularpreference by one or more C₃-C₈ alkylene bridges, or by one or moreC₂-C₁₂ alkylated azo bridges, in particular by one or more C₄-C₁₀alkylated azo bridges.

Furthermore, identical or different compounds of the formulae Ia and Ibmay also be connected by bridges of the formula II

where Y is silicon or germanium and R³ and R⁴ are hydrogen and/or C₁-C₁₂alkyl. For this purpose it is preferred to use silicon-based bridges.

Selected ligands of the formula Ia which are especially suitable arepictured below as formulae Ia₁ to Ia₁₇:

Particularly suitable ligands of the formula Ib are pictured below asformulae Ib₁ and Ib₂:

Particularly suitable ligands composed of two or more bridge-connectedcompounds of the formula Ia are pictured below as formulae Ia_(I) andIa_(II).

The synthesis of the ligands of the formulae Ia and Ib is known per se.Synthesis procedures for such ligands can be found, inter alia, in DE-A2923206, EP-A 046331, EP-A 046328, and EP-A 052929.

The ligands Ia and Ib can be used in mixtures in ratios from 0:100 to100:0 mol %. Preferred embodiments are 0:100 mol %, 10:90 mol %, 50:50mol %, 90:10 mol % and 100:0 mol %.

The ligands of the formulae Ia and Ib are combined with a phosphinecompound PR′₃, where R′ is hydrogen, C₁-C₁₂ alkyl, C₄-C₁₂ cycloalkyl,C₇-C₁₅ aralkyl or C₆-C₁₅ aryl groups.

For examples of particularly preferred substituents, refer to thelistings for the radical R in the formulae Ia and Ib.

A particularly preferred phosphine compound used is triphenylphosphine.

Instead of the phosphine compound PR′₃ it is also possible to use thediphosphine compound R₁₂P-G-PR′₂, where R′ has the same definition asfor the phosphine compounds PR′₃ and G stands for C₁-C₁₂ alkyl, C₄-C₁₂cycloalkyl, C₇-C₁₅ aralkyl or C₆-C₁₅ aryl groups.

Phosphine compounds of these kinds can be prepared in accordance withcustomary syntheses of organic chemistry and are also availablecommercially.

As well as with the phosphine compound, the ligands of the formulae Iaand Ib are also combined with one or more metal compounds of the formulaM(L²)₂ or M(L²)₂(L¹)_(z). In these formulae the variables are defined asfollows:

-   L¹ is selected from phosphanes of the formula (R⁵)_(x)PH_(3-x) or    amines of the formula (R⁵)_(x)NH_(3-x), where x is an integer    between 0 and 3. However, ethers (R⁵)₂O such as diethyl ether or    tetrahydrofuran, H₂O, alcohols (R⁵)OH such as methanol or ethanol,    pyridine, pyridine derivatives of the formula C₅H_(5-x)(R⁵)_(x)N,    such as 2-picoline, 3-picoline, 4-picoline, 2,3-lutidine,    2,4-lutidine, 2,5-lutidine, 2,6-lutidine or 3,5-lutidine, CO, C₁-C₁₂    alkyl nitriles or C₆-C₁₄ aryl nitriles, are also suitable, such as    acetonitrile, propionitrile, butyronitrile or benzonitrile. It is    additionally possible for ethylenically mono- or polyunsaturated    double bond systems to serve as ligands, such as ethenyl, propenyl,    cis-2-butenyl, trans-2-butenyl, cyclohexenyl or norbornanyl.-   R⁵ is selected from hydrogen, C₁-C₂₀ alkyl groups, which may in turn    be substituted by O(C₁-C₆ alkyl) or N(C₁-C₆ alkyl)₂ groups, C₃-C₁₂    cycloalkyl groups, C₇-C₁₃ aralkyl radicals, and C₆-C₁₄ aryl groups;    specific examples of these groups can be found in the definition of    the radical R.-   L² is selected from    -   halide ions such as fluoride, chloride, bromide, or iodide,        preferably chloride and bromide,    -   amines (R⁶)_(x)NH_(3-x), where x is an integer between 0 and 3        and R⁶ is C₁-C₁₂ alkyl,    -   C₁-C₆ alkyl anions such as Me—, (C₂H₅)—, (C₃H₇)—, (n-C₄H₉)—,        (tert. —C₄H₉)— or (C₆H₁₄)—;    -   allyl anions or methallyl anions,    -   benzyl anions, or    -   aryl anions such as (C₆H₅)—.-   M is a transition metal from groups 7 to 10 of the Periodic System    of the Elements; preference is given to manganese, iron, cobalt,    nickel or palladium, and particular preference to nickel.-   z is an integer from 0 to 4.

In one particular embodiment L¹ and L² are linked to one another by oneor more covalent bonds. Examples of such ligands are 1,5-cyclooctadienyl(“COD”), 1,6-cyclodecenyl, and 1,5,9-all-trans-cyclododecatrienylligands.

In a further particular embodiment L¹ is tetramethylethylenediamine.

Especially preferred metal compounds are Ni(COD)₂ and Ni(CH₃)₂(TMEDA).

The conditions for the reaction of the ligand or ligands of the formulaeIa and Ib with the metal compound and with the phosphine compound arenot critical per se. They are commonly reacted at from 0 to 100° C. in asolvent selectable from aliphatic and aromatic hydrocarbons such as, forexample, n-heptane, toluene, ethylbenzene, ortho-xylene, meta-xylene orpara-xylene. Chlorobenzene as well is a suitable solvent, and alsoketones such as acetone, cyclic or noncyclic ethers such as diethylether, diisopropyl ether, 1,4-dioxane or tetrahydrofuran, water oralcohols such as methanol or ethanol, for example. Molar ratios of metalcompound to phosphine compound which have been found suitable are from1:1000 to 1000:1, preferably from 1:10 to 10:1, and with particularpreference from 1:2 to 2:1. The molar ratio of the ligand or ligands Iaor Ib to the phosphine compound is likewise from 1:1000 to 1000:1,preferably from 1:10 to 10:1, in particular from 1:2 to 2:1.

It is possible here to react the metal compound with the chosen organicligand and the phosphine compound outside of the polymerization reactorand then to introduce the reaction solution into the polymerizationreactor.

The reaction of metal compound, phosphine compound, and ligand may alsotake place within the polymerization reactor, in which case it may be ofadvantage to add other substances at this point as well, such as furthersolvents, monomers for polymerization, and other auxiliaries, such asactivators or emulsifiers, for example.

The choice of reaction conditions depends in each case on the substancesused. Particularly in the case of precursors sensitive to water it hasproven advantageous to react the precursors outside of thepolymerization reactor first and then to meter the reaction product intothe polymerization reactor.

This approach is likewise advantageous when the precursors do notdissolve fully in the solvent used, but of course the reaction productdoes.

The complexes formed in situ are not isolated and purified.

The complexes produced in situ are ideally suited to use in thepolymerization or copolymerization of olefins in water or in a solventmixture with a water content of at least 50% by volume. Thepolymerization is conducted optionally in the presence of an activatorand optionally in the presence of an emulsifier.

It is further advisable to use an activator in addition in order toincrease the activity. The activator may comprise olefin complexes ofrhodium or of nickel.

Preferred nickel-(olefin)_(y) complexes, available commercially fromAldrich, are Ni(C₂H₄)₃, Ni(1,5-cyclooctadiene)₂ or “Ni(COD)₂”,Ni(1,6-cyclodecadiene)₂, and Ni(1,5,9-all-trans-cyclododecatriene)₂.Particular preference is given to Ni(COD)₂.

Mixed ethylene/1,3-dicarbonyl complexes of rhodium are particularlysuitable, for example, rhodium acetylacetonate ethylene orRh(acac)(CH₂═CH₂)₂, rhodium benzoylacetonate-ethyleneRh(C₆H₅—CO—CH—CO—CH₃)(CH₂═CH₂)₂, or Rh(C₆H₅—CO—CH—CO—C₆H₅)(CH₂═CH₂)₂.The most suitable is Rh(acac)(CH₂═CH₂)₂. This compound can besynthesized in accordance with the formulation of R. Cramer from Inorg.Synth. 1974, 15, 14.

In some cases, activation can be brought about by ethylene. Thereadiness of the activating reaction depends critically on the nature ofthe ligand L¹. Thus it has been possible to show that, when L¹ is, forexample, a tetramethylethylenediamine ligand, there is no need for anactivator.

The polymerization of the 1-olefins by the process of the invention maybe conducted in a manner known per se.

The sequence of addition of the reagents during the polymerization isnot critical. For instance, first of all gaseous monomer can be injectedinto the solvent or liquid monomer metered in, and the mixture ofligand, phosphine compound, and metal compound added subsequently.Alternatively, the mixture of ligand, phosphine compound, and metalcompound can first be diluted with further solvent and then monomer canbe added.

At the same time the activator, where necessary, is dissolved in asecond portion of the same solvent or else in acetone.

The polymerization itself normally runs at a minimum pressure of 1 bar;below this pressure, the polymerization rate is too low. Preference isgiven to 2 bar and particular preference to a minimum pressure of 10bar.

4000 bar may be stated as a maximum pressure; at higher pressures, therequirements imposed on the material from which the polymerizationreactor is constructed are very stringent, and the process becomesuneconomic. Preference is given to 100 bar and particular preference to50 bar.

The temperature of polymerization may be varied within a wide range. 10°C. may be specified as a minimum temperature, since at low temperaturesthe polymerization rate declines. Preference is given to a minimumtemperature of 40° C. and with particular preference 65° C. A sensiblemaximum temperature is 350° C. and preferably 150° C., with particularpreference 100° C. Suitable organic solvents include aromatic solventssuch as benzene, toluene, ethylbenzene, ortho-xylene, meta-xylene, andpara-xylene, and also mixtures thereof. Also suitable are cyclic etherssuch as tetrahydrofuran and dioxane or acyclic ethers such as diethylether, di-n-butyl ether, di-isopropyl ether or 1,2-dimethoxyethane.Ketones as well, such as acetone, methyl ethyl ketone or diisobutylketone, are suitable, as are amides such as dimethylformamide ordimethylacetamide. Mixtures of these solvents with one another aresuitable, furthermore, as are mixtures of these solvents with water oralcohols such as methanol or ethanol.

Preference is given to acetone and water and to mixtures of acetone andwater, the mixing ratio being arbitrary.

The amount of the solvent is likewise not critical, although it isnecessary to ensure that the complex formed in situ and the activatorcan be dissolved completely; otherwise, activity losses are likely. Thedissolution process may be accelerated, where appropriate, by means ofultrasound.

The emulsifier likewise to be added may be dissolved in a third portionof the solvent or else together with the ligand or the metal compound.

The amount of emulsifier is chosen such that the mass ratio betweenmonomer and emulsifier is more than 1, preferably more than 10, and withparticular preference more than 20. The smaller the amount of emulsifierthat need be used, the better.

The ligands of the formulae Ia and Ib may act per se as emulsifiers. Theactivity in the polymerization is greatly increased, however, if anadditional emulsifier is added. This emulsifier may be ionic or nonionicin nature.

Examples of customary nonionic emulsifiers are ethoxylated mono-, di-and tri-alkylphenols (EO units: 3 to 50, alkyl: C₄-C₁₂) and alsoethoxylated fatty alcohols (EO units: 3 to 80; alkyl: C₈-C₃₆). Examplesof such are the Lutensol® grades from BASF AG or the Triton® grades fromUnion Carbide.

Customary anionic emulsifiers are, for example, alkali metal salts andammonium salts of alkyl sulfates (alkyl: C₈ to C₁₂), of sulfuricmonoesters with ethoxylated alkanols (EO units: 4 to 30, alkyl: C₁₂-C₁₈)and with ethoxylated alkylphenols (EO units: 3 to 50, alkyl: C₄-C₁₂), ofalkylsulfonic acids (alkyl: C₁₂-C₁₈), and of alkylarylsulfonic acids(alkyl: C₉-C₁₈)

Suitable cationic emulsifiers are generally C₆-C₁₈-alkyl-, -aralkyl- orheterocyclyl-containing primary, secondary, tertiary or quaternaryammonium salts, alkanolammonium salts, pyridinium salts, imidazoliniumsalts, oxazolinium salts, morpholinium salts, thiazolinium salts, andalso salts of amine oxides, quinolinium salts, isoquinolinium salts,tropylium salts, sulfonium salts, and phosphonium salts. Examples thatmay be mentioned include dodecylammonium acetate or the correspondinghydrochloride, the chlorides or acetates of the various2-(N,N,N-trimethylammonium)ethylparaffinic esters, N-cetylpyridiniumchloride, N-laurylpyridinium sulfate, andN-cetyl-N,N,N-trimethylammonium bromide,N-dodecyl-N,N,N-trimethylammonium bromide,N,N-distearyl-N,N-dimethylammonium chloride, and the gemini surfactantN,N′-(lauryldimethyl)ethylenediamine dibromide. Numerous furtherexamples can be found in H. Stache, Tensid-Taschenbuch,Carl-Hanser-Verlag, Munich, Vienna, 1981 and in McCutcheon's,Emulsifiers & Detergents, MC Publishing Company, Glen Rock, 1989.

As the polymerization reactor, stirred tanks and autoclaves and alsotube reactors have proven useful, it being possible for the tubereactors to be configured as loop reactors.

The monomer or monomers to be polymerized is or are mixed in thepolymerization medium. The polymerization medium used may comprise wateror mixtures of water with the solvents listed above. It should beensured that the fraction of water is at least 50% by volume, based onthe total mixture, preferably at least 90% by volume, and withparticular preference at least 95% by volume.

The solutions of the complex generated in situ, of the activator whereappropriate, and of the emulsifier where appropriate, are combined withthe mixture of monomer and aqueous polymerization medium. The sequencein which the various components are added is not critical per se. It is,however, necessary for the components to be combined with sufficientrapidity that there is no crystallization of any low-solubility complexintermediates that may be formed.

Suitable polymerization methods include in principle both continuous andbatchwise methods. Preference is given to semicontinuous methods(semibatch methods), in which, after all the components have been mixed,monomer or monomer mixtures are metered in supplementarily in the courseof the polymerization.

The process of the invention initially produces aqueous polymerdispersions.

The average diameters of the polymer particles in the dispersions of theinvention are between 10 and 1000 nm, preferably between 50 and 500 nm,and with particular preference between 70 and 350 nm. The distributionof the particle diameters may, but need not necessarily, be veryuniform. For certain applications, particularly for those with highsolids contents (>55%), broad or bimodal distributions are in factpreferred.

The aqueous dispersions of the invention may also be present in the formof a miniemulsion, which means that the emulsified particles have adiameter of from 50 nm to 150 nm, in particular from 70 nm to 100 nm. Toprepare such a miniemulsion the emulsified particles are subjected tostrong shearing. Strong shearing of this kind can be achieved, interalia, by means of high-pressure homogenization, ultrasound or else jetdispersers. It is preferred in this case to operate with ultrasound.

The polymers obtained by the process of the invention have industriallyadvantageous properties. In the case of polyethylene, they may exhibit ahigh degree of crystallinity, something which can be demonstrated, forexample, by the number of branchings. Frequently less than 40branchings, preferably less than 20 branchings, and with particularpreference less than 10 branchings are found per 1000 carbon atoms inthe polymer, as determined by ¹H-NMR and ¹³C-NMR spectroscopy.

The molecular weight distributions of the polyolefins obtainable by theprocess of the invention, i.e., the Q values, are situated between 1.0and 50 and, preferably, between 1.5 and 10. The molar masses of thepolyolefins obtained are situated within the range from 1000 to 1 000000, in particular in the range from 100 000 to 3000 (numericalaverages).

An advantage of the dispersions of the invention, in addition to thefavorable price arising from the inexpensive monomers and process, isthat they are more stable to weathering than dispersions ofpolybutadiene or butadiene copolymers. As compared with dispersions ofpolymers comprising acrylates or methacrylates as principal monomer, thereduced tendency toward hydrolysis is an advantage. A further advantageis that the majority of olefins are highly volatile and unpolymerized,residual monomers are easily removed. Finally, it is an advantage thatthere is no need to add molar mass regulators during the polymerization,such as tert-dodecyl mercaptan, for example, which first are difficultto separate off and secondly have an unpleasant odor. It is alsofavorable that the aqueous dispersions obtained from the process of theinvention have relatively high solids contents of up to 20%.

From the aqueous dispersions obtained initially, the polymer particlesper se can be obtained by removing the water and, where present, theorganic solvent or solvents. A large number of common techniques aresuitable for such removal, examples including filtration, spray dryingor evaporation. The polymers thus obtained have a good morphology and ahigh bulk density.

The particle size can be determined by light scattering methods. Anoverview can be found in D. Distler (editor) “Wä{umlaut over ( )}BrigePolymerdispersionen”, Wiley-VCH Verlag, 1st edition, 1999, chapter 4.

The dispersions prepared in accordance with the invention can be usedadvantageously in numerous applications, such as paper applications suchas paper coating or surface sizing, and also paints and varnishes,construction chemicals, adhesive base materials, foam moldings,applications to textiles and leather, coatings for carpet backings,mattresses or pharmaceutical applications.

By paper coating is meant the coating of the paper surface with aqueouspigmented dispersions. The dispersions prepared in accordance with theinvention are advantageous on account of their favorable price. Surfacesizing is the pigment-free application of hydrophobicizing substances.As particularly hydrophobic substances, the polyolefin dispersionsspecifically are of advantage, having been difficult to obtain to dateunder economic conditions. A further advantage is that, during theinventive preparation of the dispersions for paper coating or surfacesizing, there is no need to add any molar mass regulators such astert-dodecyl mercaptan, for example, which on the one hand are difficultto separate off and on the other hand have an unpleasant odor.

In paints and varnishes, the dispersions prepared in accordance with theinvention are particularly suitable on account of their favorablepricing. Of particular advantage are aqueous polyethylene dispersions,since they additionally possess high UV stability. Moreover, aqueouspolyethylene dispersions are particularly suitable on account of theirresistance to basic chemicals, which are customary in the constructionindustry.

In adhesives, particularly in adhesives for self-adhesive labels orfilms and also patches, but also in construction adhesives or industrialadhesives, the dispersions prepared in accordance with the inventionhave economic advantages. In construction adhesives in particular theyare especially favorable, since they are resistant to basic chemicals,which are common in the construction industry.

In foam moldings, which can be produced from the dispersions prepared inaccordance with the invention by processes which are known per se, suchas the Dunlop process or the Talalay process, the favorable price of theinventive dispersions is again of advantage. Further components includegelling agents, soaps, thickeners, and vulcanizing pastes. Foam moldingsare processed, for example, into mattresses.

Applications made to textiles and leather serve to preserve and ennobletextile or leather. Examples of the effects imparted includeimpregnation and further finishing of the textiles. An advantageousfeature of the dispersions prepared in accordance with the invention,when used as part of applications to textiles and leather, in additionto the favorable price, is the freedom from odor, since residual olefinmonomers are easily removed.

Coatings on carpet backing serve to bond the carpet fibers to thebacking, and also have the function of giving the carpet the necessarystiffness and of effecting uniform distribution of additives such asflame retardants or antistats, for example. An advantageous feature ofthe dispersions prepared in accordance with the invention, besides thefavorable price, is their lack of sensitivity to the customaryadditives. Polyethylene dispersions in particular have provenparticularly inert chemically. A final advantage is that, during thepreparation of the dispersions in accordance with the invention forcoatings on carpet backings, there is no need to add molar massregulators such as tert-dodecyl mercaptan, for example, which on the onehand are difficult to separate off and on the other hand have anunpleasant odor.

By pharmaceutical preparations are meant dispersions as vehicles fordrugs. Dispersions as drug vehicles are known per se. An advantage ofthe dispersions prepared in accordance with the invention as drugvehicles is the economically favorable price and the resistance tophysiological influences such as gastric fluid or enzymes.

WORKING EXAMPLES

General notes: The syntheses, unless otherwise described, were carriedout in accordance with the Schlenk technique in the absence of air andmoisture.

The molar masses of the polymers obtained were determined by means ofGPC.

In accordance with DIN 55672, the conditions chosen were as follows:solvent: 1,2,4-trichlorobenzene; flow rate: 1 ml/min; temperature: 140°C. Measurement was carried out on a Waters 150C instrument which hadbeen calibrated using polyethylene standards.

The solids content was determined by precipitating the polyethylene frommethanol.

Example 1 Starting from 2,3,5,6-tetrachloro-p-benzoquinone

64 mg (258 μmol) of 2,3,5,6-tetrachloro-p-benzoquinone and 68 mg (258μmol) of triphenylphosphine were dissolved in 1 ml of methanol (driedand degassed), 4 ml of toluene (dried and degassed) and 0.3 ml ofhexadecane (degassed). The solution obtained was stirred for 20 minutes,during which it turned orange in color. The solution was then introducedinto another Schlenk flask, which contained 79 mg (287 μmol; 1.11 eq) ofnickel-(cyclooctadiene)₂ [Ni(cod)₂].

In the interim, a solution of 1 g of sodium dodecyl sulfate [SDS] in 95ml of degassed and deionized water was prepared. 75 ml of this aqueoussolution were introduced directly into the reactor, the other 20 ml wereadded to the catalyst mixture and subjected to ultrasound treatment (120W, 2 minutes). The miniemulsion obtained in this way was then introducedinto the reactor using a hollow Teflon needle.

The reactor was subsequently filled with ethylene, setting a constantethylene pressure of 40 bar, and at the same time the interior of thereactor was heated to 70° C. with stirring (1000 rpm). After a reactiontime of 2 hours, the polymerization was terminated by cooling andreleasing the ethylene.

The aqueous latex obtained had a solids content of 18% (determined byprecipitating 7.1 g of polyethylene from the latex using 40 ml ofmethanol). The polyethylene obtained had a molar mass (number-average)of 6200, the weight average being approximately 18 000.

Example 2 Starting from 2,3,5,6-tetrachloro-p-benzoquinone

64 mg (258 μmol) of 2,3,5,6-tetrachloro-p-benzoquinone and 68 mg (258μmol) of triphenylphosphine were dissolved in 1 ml of methanol (driedand degassed), 4 ml of toluene (dried and degassed) and 0.3 ml ofhexadecane (degassed). The solution obtained was stirred for 20 minutes,during which it turned orange in color. The solution was then introducedinto another Schlenk flask, which contained 79 mg (287 μmol; 1.11 eq) ofnickel-(cyclooctadiene)₂ [Ni(cod)₂].

In the interim, a solution of 1 g of SDS in 95 ml of degassed anddeionized water was prepared. 75 ml of this aqueous solution wereintroduced directly into the reactor, the other 20 ml were added to thecatalyst mixture and subjected to ultrasound treatment (120 W, 2minutes). The miniemulsion obtained in this way was then introduced intothe reactor using a hollow Teflon needle.

The reactor was subsequently filled with but-1-ene, setting a constantbut-1-ene pressure of 10 bar, and at the same time the interior of thereactor was heated to 70° C. with stirring (1000 rpm). After 30 minutesthe but-1-ene was replaced by ethylene, which was under a constantpressure of 40 bar.

After a further reaction time of 1.5 hours, the polymerization wasterminated by cooling and releasing the ethylene.

The aqueous latex obtained had a solids content of 8% (determined byprecipitating 13.01 g of copolymer of ethylene and but-1-ene from thelatex using methanol).

Example 3 Starting from 2,3,5,6-tetrabromo-p-benzoquinone

64 mg (258 μmol) of 2,3,5,6-tetrabromo-p-benzoquinone and 68 mg (258μmol) of triphenylphosphine were dissolved in 1 ml of methanol (driedand degassed), 4 ml of toluene (dried and degassed) and 0.3 ml ofhexadecane (degassed). The solution obtained was stirred for 20 minutes,during which it turned orange in color. The solution was then introducedinto another Schlenk flask, which contained 79 mg (287 μmol; 1.11 eq) ofNi(cod)₂.

In the interim, a solution of 1 g of SDS in 95 ml of degassed anddeionized water was prepared. 75 ml of this aqueous solution wereintroduced directly into the reactor, the other 20 ml were added to thecatalyst mixture and subjected to ultrasound treatment (120 W, 2minutes). The miniemulsion obtained in this way was then introduced intothe reactor using a hollow Teflon needle.

The reactor was subsequently filled with ethylene, setting a constantethylene pressure of 40 bar, and at the same time the interior of thereactor was heated to 40° C. with stirring (1000 rpm). After a reactiontime of 2 hours, the polymerization was terminated by cooling andreleasing the ethylene.

The aqueous latex obtained had a solids content of 9% (determined byprecipitating 3.4 g of polyethylene from the latex using 40 ml ofmethanol).

1. A process for emulsion polymerization of one or more olefins,comprising: i) preparing a catalyst by reacting a) a ligand of theformula Ia or Ib or a mixture of at least two of the ligands Ia or Ibwith b-1) a phosphine compound PR′₃, wherein R′ is hydrogen, C₁-C₁₂alkyl, C₄-C₁₂ cycloalkyl, C₇-C₁₅ aralkyl or C₆-C₁₅ aryl group, and c) ametal compound of the formula M(L²)₂ or M(L²)₂(L¹)_(z), wherein theformulas of the ligands Ia and Ib (a) are as follows:

wherein each R substituent represents one or more of the followingradicals: hydrogen, halogen, nitrile; or C₁-C₁₂ alkyl, C₁-C₁₂ alkoxy,C₇-C₁₃ aralkyl, C₆-C₁₄ aryl groups, each optionally substituted byC₁-C₁₂ alkyl groups, halogens, C₁-C₁₂ alkoxy, C₃-C₁₂ cycloalkyl, C₁-C₁₂thioether groups, or carboxyl groups or sulfo groups, each being in itsacid or salt form, or amino and/or C₁-C₁₂ alkyl substituted aminogroups; amino groups NR¹R², where R¹ and R² together or separately arehydrogen, C₁-C₁₂ alkyl, C₇-C₁₃ aralkyl or C₆-C₁₄ aryl groups and mayadditionally form a saturated or unsaturated 5- to 10-membered ring,unsubstituted or substituted by C₁-C₁₂ alkyl groups, halogens, C₁-C₁₂alkoxy, C₃-C₁₂ cycloalkyl, C₁-C₁₂ thioether groups, or carboxyl groupsor sulfo groups, each being in its acid or salt form, or amino and/orC₁-C₁₂ alkyl substituted amino groups; and wherein identical ordifferent compounds of the formulae Ia and Ib optionally are bridged byone or more C₁-C₁₂ alkylene, C₂-C₁₂ alkylated azo or formula II bridgingmoieties, said formula II having the structure:

 wherein Y is silicon or germanium and R³ and R⁴ are hydrogen and/orC₁-C₁₂ alkyl; and wherein the definitions of the metals and L groups inthe metal compounds are as follows: M is a transition metal selectedfrom the group consisting of Groups 7 to 10 of the Periodic Chart of theElements; L¹ is phosphanes (R⁵)_(x)PH_(3-x) or amines (R⁵)_(x)NH_(3-x)with identical or different radicals R⁵, ethers (R⁵)₂O, H₂O, alcohols(R⁵)OH, pyridine, pyridine derivatives of the formulaC₅H_(5-x)(R⁵)_(x)N, CO, C₁-C₁₂ alkyl nitriles, C₆-C₁₄ aryl nitriles orethylenically unsaturated double bond systems, x being an integer from 0to 3; R⁵ is hydrogen, C₁-C₂₀ alkyl groups, which may in turn besubstituted by O(C₁-C₆ alkyl) or N(C₁-C₆ alkyl)₂ groups, C₃-C₁₂cycloalkyl groups, C₇-C₁₃ aralkyl radicals, or C₆-C₁₄ aryl groups, L² ishalide ions or R⁶ _(x)NH_(3-x), where x is an integer from 0 to 3 and R⁶is C₁-C₁₂ alkyl or C₁-C₆ alkyl anions, allyl anions, benzyl anions oraryl anions, and optionally L¹ and L² being linked to one another by oneor more covalent bonds; and z is a number from 0 to 4; and ii)immediately (co)polymerizing one or more olefins in water or a solventmixture with a water content of at least 50% by volume in the presenceof an emulsifier and, optionally, of an activator.
 2. A process asclaimed in claim 1, wherein one or more olefins are emulsion polymerizedas a miniemulsion in water, produced with the aid of ultrasound.
 3. Aprocess as claimed in claim 1, wherein said activator is present in the(co)polymerization medium.
 4. A process as claimed in claim 3, whereinsaid activator is an olefin complex of rhodium or of nickel.
 5. Aprocess as claimed in claim 3, wherein said emulsifier is an ionicemulsifier.
 6. A process as claimed in claim 1, wherein one of saidolefins is ethylene.
 7. A process as claimed in claim 1, wherein oneolefin is ethylene and the comonomer is selected from propylene,1-butene, 1-hexene and styrene.
 8. A process as claimed in claim 1,wherein the olefin for polymerization is ethylene.
 9. The process asclaimed in claim 1, wherein said ligands Ia to Ib are combined in aratio of 10:90 to 90 to 10 mole %.
 10. The process as claimed in claim1, wherein the metal compound is combined with the phosphine in a molarratio ranging from 1:1000 to 1000:1.
 11. The process as claimed in claim1, wherein the ligand Ia or Ib is combined with the phosphine compoundin a molar ratio ranging from 1:1000 to 1000:1.